1. Field of the Invention
The present invention relates to a cleaning device that removes foreign matter adhering to a surface of a surface moving member (i.e., a member having a moving surface). The present invention further relates to an image forming apparatus, such as a copier, a printer, and a facsimile machine, a process cartridge, and an intermediate transfer unit, each of which includes the cleaning device.
2. Description of the Related Art
There is a wide variety of image forming apparatuses, such as electrophotographic image forming apparatuses and inkjet image forming apparatuses, and many of which are provided with surface moving members. For example, some of the electrophotographic image forming apparatuses are provided with surface moving members including a latent image carrying member (i.e., image carrying member), such as a photoconductor drum; an intermediate transfer member (i.e., image carrying member), such as an intermediate transfer belt; and a recording medium conveying member, such as a sheet conveying belt. Further, some inkjet image forming apparatuses are provided with surface moving members including a recording medium conveying member, such as a sheet conveying belt. In general, unnecessary foreign matter adhering to a surface of such a surface moving member causes a variety of problems. Therefore, a cleaning device is used that removes the unnecessary foreign matter from the surface of the surface moving member as a cleaning target.
Related-art cleaning devices that clean a surface of the cleaning target include a cleaning device using a blade member formed by an elastic member made of, for example, urethane rubber molded into a plate shape. In such a cleaning device, the blade member is held by a holding member made of a highly rigid material, such as metal, and fixed to the fixed to the frame of the device, and one end of the blade member is pressed against the surface of the cleaning target to remove the foreign matter adhering to the surface. Such a cleaning device is simple in configuration and low in cost, and exhibits high foreign matter removal performance, and thus is widely used.
In the cleaning device according to the blade cleaning method, it is desired to bring the blade member into contact with the surface of the cleaning target with relatively high contact pressure to obtain high removal performance. It is also desired to maintain the initial contact state of the blade member to obtain stable removal performance over time.
In a single-layer blade member, the entirety of which is made of a uniform elastic material, however, it is difficult to attain both relatively high contact pressure and maintenance of the initial contact state for the following reason.
That is, if a single-layer blade member made of an elastic material of relatively high hardness is used, an edge portion of the blade member in contact with the cleaning target has a relatively small amount of deformation, and an increase in contact area of the blade member in contact with the cleaning target is suppressed. It is therefore possible to set relatively high contact pressure, and to improve the cleaning performance. In general, however, an elastic material of relatively high hardness has a relatively high permanent set value. Since the blade member is in contact with the cleaning target, with one end thereof pressed and flexed against the surface of the cleaning target, if the blade member made of an elastic material having a relatively high permanent set value is kept in continuous contact with the cleaning target for an extended period of time, so-called loss of resilience occurs, i.e., the blade member is substantially permanently deformed in a flexed shape. As a result, the contact state of the blade member over time deviates from the initial contact state, and causes cleaning failure.
By contrast, an elastic material of relatively low hardness generally has a relatively low permanent set value. Therefore, if a single-layer blade member made of an elastic material of relatively low hardness is used, the blade member is relatively resistant to the loss of resilience even if the blade member is kept in continuous contact with the cleaning target for an extended period of time, and the initial contact state can be maintained. However, an edge portion of the blade member in contact with the cleaning target is substantially deformed. Thus, the contact area is increased, and the contact pressure is reduced. As a result, sufficient removal performance is not obtained.
Thus, as described above, in a single-layer blade member, it is difficult to attain both relatively high contact pressure and maintenance of the initial contact state, and to stably obtain high removal performance over time.
Another related-art cleaning device in known, which uses a double-layer laminated blade member made of elastic materials mutually different in hardness. An edge layer of the blade including an edge portion that comes into contact with the cleaning target is made of a material of relatively high hardness, and a backing layer not in contact with the cleaning target is made of a material of relatively low hardness. With the edge layer of relatively high hardness, the edge portion in contact with the cleaning target has a relatively small amount of deformation, and an increase in contact area is suppressed, as in the above-described single-layer blade member made of an elastic material of relatively high hardness. Accordingly, relatively high contact pressure can be set. Further, the backing layer not in contact with the cleaning target has relatively low hardness and a relatively low permanent set value. Accordingly, the blade member is more resistant to the loss of resilience than the single-layer blade member of relatively high hardness, and is capable of maintaining the initial contact state.
FIG. 1 illustrates a schematic view of the blade member provided in the above-described related-art cleaning device. FIG. 1 is a diagram of a double-layer laminated blade member 15 and a blade holder 13 holding the blade member 15. The blade member 15 includes an edge layer 11 made of an elastic material of relatively high hardness and a backing layer 12 made of an elastic material of relatively low hardness.
In the blade member 15 illustrated in FIG. 1, the edge layer 11 having a relatively high permanent set value extends over an entire area from a holding position 15a held by the blade holder 13 to the leading end of the blade member 15 on the side of an edge portion 11e. Therefore, in a state in which the blade member 15 is pressed and flexed against a cleaning target, not only the backing layer 12, which is relatively resistant to the loss of resilience, but also the edge layer 11, which is relatively susceptible to the loss of resilience, is flexed. If the blade member 15 is kept in continuous contact with the cleaning target for an extended period of time, therefore, a substantial loss of resilience may occur only in the edge layer 11.
If the loss of resilience occurs in the edge layer 11, the edge layer 11 tends to maintain the flexed shape thereof. Thus, the backing layer 12 with little or no loss of resilience receives force acting in the flexing direction. Therefore, the change over time in contact state occurs more easily than in the single-layer blade member made solely of the same material as the material forming the backing layer 12.
Therefore, even if the cleaning device is designed to use the double-layer laminated blade member 15 including the edge layer 11 of relatively high hardness and the backing layer 12 of relatively low hardness, it is difficult in some cases to sufficiently maintain the initial cleaning performance, depending on the combination of the material forming the edge layer 11 and the material forming the backing layer 12.